A trend which has been observed in the development of new electrochemical accumulator systems are battery concepts in which the batteries are operated at higher temperatures above room temperature. Advantages of such battery concepts as compared to lithium-ion batteries, for example, relate primarily to the increased safety, the lower costs, and an increased energy density as compared to conventional lithium-ion batteries. Background for the elevated temperature level is the possibility for providing an at least sufficiently high conductivity of the components involved (e.g., electrolyte, protective layers) and for implementing sufficiently high exchange current densities in combination with the electrochemical cell reactions involved. Such battery concepts may need to be heated during operation or during start-up, but they potentially require no cooling capacity or only very little cooling capacity for this purpose during operation.
Such battery concepts generally also require a cooling concept, since heat is generated during operation, which may lie above the thermal losses in the system, and specific temperature limits of the cells must generally also be observed. Depending on the temperature level and operating mode, a more or less complex thermal insulation of the battery cells is required in order to keep the thermal losses low and to keep the required heat output preferably low. In this case, connection lines, mechanical supports, and other thermal bridges as well as the radiation losses which are present are potential and undesirable heat leaks. These thermal power losses negatively affect the battery performance and self-discharge, which usually must be rectified with the aid of supplied energy.
During downtimes of these battery concepts without operation or only with limited operation (e.g., a parking vehicle), heating is always required in order to be prepared for the further operation of the battery in the range of the optimal working temperature. This costs energy and may discharge the battery. There is also the possibility, during downtimes, for allowing the battery to cool down and to be heated back up to the optimal operating temperature before the next start-up. A battery which has cooled down, i.e., which is at room temperature, is mostly incapable of heating itself up, since the kinetics of the cell reaction and the internal power processes are still too limited.
German Patent Application No. DE 10 2012 223 054 A1 describes one possibility for the thermal management of a vehicle battery, in which the conditioning of the operating temperature of the battery takes place during the vehicle operation. The adaptation of the operating temperature range during operation or while the battery is connected to the charging device and to the current source is used in this case for preconditioning as a function of the ambient temperature. The disadvantage of the conventional approaches is the absence of the possibility for holding the battery at operating temperature during standing phases and for thereby dispensing with an external energy source for the thermal activation of the battery. The related art therefore lacks an approach for the energy-saving thermal management or thermal activation of the battery, the self-sufficiency of the batteries, in particular, being increased and, therefore, longer standing phases of the vehicles being made possible.